Trium specifications

Cost: �350 Memory: 16 megabytes Screen: 240 by 320 pixels Weight: 200 grammes Size: 130 mm by 90mm by 23mm Battery life: 3 hours talktime, 100 hours standby

Makers of handheld computers and phones have long been promising to produce gadgets that roll functions typically split between several devices into one package.

For years Nokia has been producing a range of communicators that combine phone and personal digital assistant but they have not been hugely popular because they are both bulky for a mobile but fiddly for a computer.

This year Ericsson produced its R380 that is a combination palmtop computer and mobile phone. Handspring has launched an expensive add on for its Visor handheld that turns it into a mobile phone. Microsoft is also making a combination device called Stinger that is due to appear soon.

But one of the big problems facing the makers of handheld computers is the speed with which mobile technologies develop. Devices produced to work with one technology can be out of date quickly if they are released long before the phone networks adopt standards that make data much easier to use on the move.

The Ericsson R380 has been criticised because it does not take advantage of the General Packet Radio Service that many mobile operators are using to boost the data handling capabilities of their networks. GPRS allows a mobile phone to be constantly connected to a data network and can speeds up Wap surfing.

The Wireless Application Protocol (Wap) converts webpages into an abbreviated form perfect for accessing by phone. But Wap sites and phones have not proved popular because they take so long to reach and few phones have screens large enough to display a useful amount of information.

One of the first to make a gadget that can use GPRS is Mitsubishi which this week expanded its Trium range with the Mondo - a handheld computer that also does everything a standard mobile phone does.

The handheld uses the Microsoft Pocket PC operating system and has onboard a basic word processor, e-mail program, media player, net browser and 16 megabytes of memory.

Costly gadget

The Mondo is expected to cost about �350 and currently is available on the BT Cellnet network, and then only with a contract rather than a pre-pay service plan.

The UK's other networks may start selling it as they expand their GPRS coverage.

BT Cellnet has two subscription plans for the Mondo designed for light and heavy data users. The standard tariff is �3.99 per month which BT claims works out a 2p per kilobyte.

One Wap screen or short e-mail message takes up one kilobyte. On-screen graphics warn users when they are burning up their monthly data allowance.

The premium tariff for heavy data users is �7.99 per month or �3.99 per megabyte. BT Cellnet claims that one megabyte is equal to 400 emails of 100 words or the downloading of 1,000 Wap screens.